Fix the inuse tests from the ZFS test suite.

Formerly there were 9 separate tests, all of which involved making sure that
ZFS, newfs, dumpadm, and svm wouldn't step on each others' toes. There was
also a lot of code dealing with Solaris's complicated partitioning scheme.
But in FreeBSD, this can all be much simpler. Everything goes through GEOM,
so we only need to test two assertions:

1. ZFS can't use a disk that's already in use, and
2. Something else can't use a disk that's in use by ZFS

tests/sys/cddl/zfs/tests/inuse/inuse_010_neg.ksh
Add a new testcase for assertion 1. The existing test cases were
all so complicated that it was easier to start from scratch.

tests/sys/cddl/zfs/tests/inuse/inuse_005_pos.ksh
Simplify this test case by eliminating partitions and only testing a
single pool topology.

tests/sys/cddl/zfs/tests/inuse/inuse_001_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_002_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_003_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_004_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_006_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_007_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_008_pos.ksh
tests/sys/cddl/zfs/tests/inuse/inuse_009_pos.ksh
Eliminate all other test cases

tests/sys/cddl/zfs/tests/inuse/inuse_test.sh
tests/sys/cddl/zfs/tests/inuse/Makefile Update boilerplate

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